Thanks I did not know that they have also introduced the felt spacer in the LCD3f.
I've been through (meaning I've owned them) LCD2f, LCD3f (twice), LCD-X and now LCD4.
The current LCD3f which I still have now but will be going to the new owner in a week's time, is a 2016 model which I bought used. It came with brown leather headband and suede brown pads. The pads were quite worn but comfortable when I received it and the headphone is in mint condition. I listen to this LCD3f in this condition for almost a year before I got all the hardware replaced. The hardware meaning the metal yoke, steel suspension headband and Audeze original back leather pads.
Tonal difference on changing over is very slight and any difference is attributed to the new tight fit and pads. Yes having such a drastic switch over will have some impact on the sound but it's slight. I do prefer the sound and fit after the switch over.
I did know about the felt spacer in the LCD4 and in fact you're not supposed to change the LCD4 pads yourself. Doing so can void the warranty. This needs to be done by Audeze, the supplier or the authorised dealer. I can't see how this will apply to LCD3f because LCD3f drivers are not that delicate as the LCD4 to warrant that special care.
A picture taken yesterday of the 3 and 4 before I say farewell to the 3
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